This multi-center, randomized, double-blind, placebo controlled, dose-escalation design evaluates the safety and tolerability of multiple oral doses of DMP-777 in six different dose levels; to determine PK characteristics, and to define the DMP-777 dosage level necessary to achieve sustained high-level systemic neutrophil elastase inhibition. Systemic neutrophil elastose inhibition is thought to benefit patients with cystic fibrosis by decreasing the number of toxic substances released by polymorphonuclear leukocytes into the CF airway which causes propagation of inflammatory response and lung damage.